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Salmon
smolt behavior
A challenge in many hydropower facilities is that downstream migrating fish can enter hydropower turbines where
they may be injured or killed. In the SafePass project, we explore how fish migrate under different hydraulic conditions
and use this knowledge to design solutions that prevent fish from entering turbines. To obtain this we need detailed
information on how fish behave in front of power plant intakes.
Tracking the smolts
During the spring of 2015, we used
acoustic tags and an array of receivers to follow the track of 91
salmon smolts as they passed the intake of Laudal Power Station
in the Mandal River. Minute by minute we tracked the swimming
directions and depths, providing a unique 3D dataset on the
behavior of salmonid smolts. Moreover, by hydraulic modelling
we have detailed information on hydraulic conditions such as
water velocity and turbulence experienced by each fish.
Earlier experiments have shown that the diversion of flow
between the power station and the bypass spill strongly
effects the migration route. Now we can explain why some
fish enter the intake tunnel whereas others select the safe
bypass route.
Swimming routes
The figure to the right shows three
salmon smolts that arrived at a similar position relative to the
intake, but followed different routes. Fish 25 (green track)
rapidly passed the intake area and was later recorded as it
entered the bypass in the dam 500 m downstream. Fish 100
(brown track) swam more or less directly towards the intake,
dived down (the tunnel intake is 3 m below the surface) and
rapidly disappeared into the tunnel.
The last example fish (no. 48, blue track) was tracked for one
hour. It swam towards the intake and dived down in front
of the tunnel intake. After twenty minutes, the fish apparently
changed its mind, left the intake area and safely passed over
the downstream dam.
The SafePass team of scientists is now using the hydraulic
models to understand the choices made by these three and
the other 88 salmon smolts.
Proactive partner
Thanks the pro-active approach to
environmental challenges adopted by the CEDREN partner
Agder Energy, the Mandal River has for many years been
used as a study site for the CEDREN projects EnviDORR,
GOVREP, EcoManage and SafePass.
Tracking smolt in Orkla
In May 2016, the tracking
set-up will be moved to the River Orkla in Central Norway,
where also the effects of LED lights as a repulsion measure will
also be tested.
The overall goal of both studies is to gain general knowledge
on the migration process, as a foundation for developing
effective measures in the numerous locations in Norway and
elsewhere, where fish may enter into hydropower turbines.
Contact:
torbjorn.forseth@nina.no